A man was arrested after he punched a subway conductor in the face at a Harlem station early Friday, police said.

Julio Leonardo, 30, was holding the doors of a downtown 4 train at the 125th Street station at about 12:15 a.m., cops said. When the 33-year-old conductor told him to stop, Leonardo walked over to him and punched him, police said.

The conductor punched Leonardo and the two began fighting.

Police then arrived at the scene and took Leonardo, of the Bronx, into custody. He was later charged with assault.

The conductor was treated for bruising on his nose and Leonardo was treated for a cut on his lip, cops said.

The attack was "an ugly example" of "how difficult and dangerous working in the subway can be," Transport Workers Union Local 100 President Tony Utano said in a statement.

"This was a disgusting and outrageous attack, and we will do everything we can to see that this criminal gets the punishment he deserves in court," he said.

At the same station on Thursday, a 34-year-old man was slashed in the face after he accidentally bumped into the suspect, according to ABC7.